| A | B |
|---|
| Meteorologists | collect and record weather data and use the information to forecast weather. |
| Conditions in the air | the temperature, the amount of moisture, and the presence or absence of clouds |
| Air pressure | weight of the atmosphere, it pushes in all directions in any |
| Molecules in warm air | move faster and farther apart, forming an area of low pressure |
| molecules in cool air | move slower and stay close together, forming an area of high pressure. |
| Air | moves from a region of high pressure to a region of low pressure |
| amount of water vapor | depends on its temperature; the warmer the temperature, the more water vapor the air can hold. |
| Relative humidity | amount of water vapor in air compared to the amount that the air could hold at a particular temperature |
| 100% relative humidity | water vapor condenses |
| • When a warm air mass moves into a cold air mass | warm front develops |
| Precipitation | may develop ahead of a warm front. |
| • When a cold air mass moves into a warm air mass | cold front develops |
| A front | is the boundary between warm and cold air masses. |
| • Low-pressure areas (lows – symbol L) | are usually associated with clouds and precipitation. |
| High-pressure areas (highs – symbol H) | usually associated with fair weather. |
| Hurricanes | form around very low pressure areas over warm waters |
| weather data collection | computerized and automated |
| Weather balloons | float high into the atmosphere twice daily around the world; contain sensors and radio transmitters that broadcast weather data back to ground stations |
| Doppler radar | allows meteorologists to track the movement of precipitation and winds within a storm to better predict the movement of storms and outbreaks of severe weather |
| Weather satellites | gather data such as movement of water vapor and ocean temperatures from around the world |
